Control arrangement for circuit breakers



Dec. 7, 1954 T. R. COGGESHALL. El AL CONTROL ARRANGEMENT FOR CIRCUITBREAKERS Filed Dec. 21, 1949 3 Sheets-Sheet 1 Inventors: Thellwell'RCoeshall, Nelson H.westervelt,

Their Attornqg.

1954 T. R. COGGESHALL ETAL 2,696,536

CONTROL ARRANGEMENT FOR CIRCUIT BREAKERS Filed Dec. 21, 1949 3Sheets-Shea 2 Inventors: Thellwell R. Coggeshall, Nelson H.\A/estervelt.

bps W Their- Attorne g.

Dec. 7, 1954 T. R. COGGESHALL ETAL 2,696,536

CONTROL ARRANGEMENT F OR CIRCUIT BREAKERS 3 Sheets-Sheet 5 Filed Dec.

Inventor's: Thellwe H P. Cogge shall,

Nelson H. We ster'velt Their Attorne g.

United States Patent CONTROL ARRANGEMENT FOR CIRCUIT BREAKERS ThellwellR. Coggeshall, Bala Cynwyd, and Nelson H.

Westervelt, Drexel Hill, Pa., assignors to General Electric Company, acorporation of New York Application December 21, 1949, Serial No.134,246

9 Claims. (Cl. 20089) This invention relates to control arrangements forcircuit breakers and more particularly to an arrangement for controllingan electrically operated mechanism utilized to operate circuit breakers,particularly those wh ch are of the biased open type. The invention isan improvement upon the operating mechanism control scheme disclosed inPatent 1,723,103Walle, granted August 6, 1929, and assigned to theassignee of this invention and, in certain respects, is somewhat similarto the control arrangement disclosed in copending application Serial No.68,363-Favre, filed December 30, 1948, now Patent No. 2,534,115,December 12, 1950, and assigned to the assignee of this invention.

An object of the invention is to provide an improved control arrangementfor circuit breakers which deenergizes the circuit breaker closingmeans, such as a motor or solenoid, upon completion of the closingstroke; which also provides an earlier deenergization or control cutottwhenever the circuit breaker trips free due to fault conditions existingduring a closing or reclosing stroke of the breaker; and which furtheris readily adaptable to function as a latch checking device wherebypower to reclose the breaker cannot be applied unless the trip latch issafely restored to its latching position as the proper sequel 'to anopening or a trip-free operation.

Another object of the invention is to provide an improved controlarrangement for power operating means for circuit breakers wherein thecontrolled breaker is capable of trip-free operation and whereinprovision is made for insuring that the power closing circuit cannot bereestablished until the trip latch for holding the breaker closedagainst its opening bias has reset in its safe latching posit-ionwithout any necessity for using a separate conventional so-calledlatch-checking switch for this purpose.

Still another object of the invention is to provide anelectromagnetically operated control switch for use in a circuit breakercontrol arrangement which comprises a movable switch arm together withmeans for maintaining the switch arm in its momentarily closed position,and a rotatable pivotally mounted member disposed for engagement with anabutment member so that the movable element of the electromagnetic meansis in driving relationship with the switch arm only during a switchclosing operation and is divorced therefrom thereafter as during aswitch opening operation.

In accordance with the invention, the energizing circuit for theelectrically operated power means for closing a circuit breaker iscontrolled, i. e., established and then cut ofi, by switching meanswhich, after just being closed electromagnetically, is caused to openpositively at or near the end of the closing stroke of the breaker bymechanical means actuated by the electrically operated power means. Anappropriately configured movable member disposed for movement inresponse to operation of the electrically operated closing means may beused for providing a variable cutoff characteristic for the closingcontrol switch which is very desirable for circuit breaker trip-freeoperations and which member, in addition, serves as hold-open means forthe switch thereby preventing a subsequent closing operation of thebreaker if the mechanism trip latch failed to reset to its properlatching position at the termination of the preceding opening operation.

The invention will be better understood by reference to the accompanyingdrawing wherein Fig. 1 schemati- Patented Dec. 7, 1954 cally representsthe invention with the parts in the positions which they occupy afterthe breaker is opened; Fig. 2 shows the parts in their respectivepositions during a circuit breaker closing operation; and Fig. 3 showsthe parts in their respective latched-in positions after completion of acircuit breaker closing operation.

While the drawings show the invention as applied to a solenoid operatedmechanism, the invention is equally applicable to other types ofoperating mechanism, such, for example, as motor driven mechanisms suchas that disclosed in the above mentioned Walle patent.

Referring now to Fig. l, the numeral 1 designates the operating rod forthe controlled circuit breaker and the numeral 2 designates the mainlever or output crank from the operating mechanism. Crank 2 is biased bythe tension spring 3 for counterclockwise movement about the fixed pivot4. Spring 3 biases the breaker contacts toward the open position so thata clockwise driving movement of lever 2 about the pivot 4 is necessaryto close the breaker contacts against this spring bias. Closing force isapplied to lever 2 through the operating mechanism by means of the mainsolenoid 5 and its armature 6. When solenoid 5 is energized, the upwardforce exerted by armature 6 is transmitted to lever 2 through thetrip-free or collapsible linkage system generally indicated at 7. Thelinkage 7 cooperates with the trip latch 8 which is rotatable about thepivot 9. The latch 8 is biased into engagement with the stop 10 by meansof the torsional spring 11 and, as will be observed from Figs. 2 and 3,this latch constitutes a shiftable prop for the link-age against whichbreaker opening forces react during and after a breaker closingoperation. Latch 8 is rotatable from its holding position by means ofthe armature 12 acting against tension spring 14 whenever the trippingsolenoid 13 is energized in any suitable manner as from some abnormalcurrent responsive relay or the like. The energization and cutoff of thecircuit of solenoid 5 are accomplished by the closing and reopeningrespectively of the contacts 15 and 16 of the control device of thisinvention, contact 16 being a fixed contact while contact 15 is movedinto and out of contact by two distinct actuating means respectively aswill become apparent as the description proceeds. Thus, when contact 15'is moved into engagement with contact 16, a circuit is completedthrough solenoid 5 and thereafter upward movement of armature 6 closesthe breaker by exerting a force thereon through the trip-free linkage 7,lever 2 and rod 1 in a manner very similar to that described in U. S.Patent 1,827,626 to Thumim which is assigned to the same assignee asthis present application.

The construction of the operating mechanism for the movable contact 15of the control device will now be described. The contact 15 is mountedon the switch arm 17 which in turn is pivotally mounted on the fixed pin19. Switch arm 17 is maintained in its open position by biasing means inthe form of a permanent magnet 20 which cooperates with an armature 21mounted on switch arm 17. Also, when operated to close, the switch arm17 and its contact 15 are then maintained in the closed position bymeans of another permanent holding magnet 22 which cooperates with anarmature 23 mounted on the switch arm. It will be understood that themagnets 20 and 22 constitute an equivalent for the conventionalovercenter spring arrangement whereby a movable contact continues in theposition to which last moved until shifted therefrom to anotherposition. Magnet 22 is the stronger, for it must furnish adequatecontact pressure for the closed contacts, while magnet 20 need be onlysufficient to hold the contacts safely parted in the open position.

The motive means for imparting closing movement to contact 15 and switcharm 17 comprises the electromagnet 24 and its cooperating armature 25which transmits its pull through an intermediate force-transmittingcrank 33. Armature 25 is biased toward the left against stop means 27 bytension spring 26. Energization of coil 24 results from the closing ofany suitable control means, such as the manually operable switch 28. Asis well known, automatically operable switch means arranged for rapidreclosing could be utilized instead of manually operable switch 28.Switch arm 17 is provided with an outwardly projecting flange portion29, the edges of which are adapted for engagement with the projectingends 30 and 31 of a spring member 32 coiled about the shaft 19. Thepurpose of spring 32 and projection 29 Will become apparent as thedescription proceeds. In order to relate operably the operating movementof armature 25 with the switch arm 17 during switch closing operation,an intermediary member comprising the actuating crank 33 is pivotallysupported on the fixed fulcrum pin 19 and is provided with an outwardlypro ecting flange portion 34 which, like flange portion 29, is normallyin engagement with the ends 30 and 31 of spring 32. Thus, due to thearrangement of spring 32 and its projecting ends 30 and 31 with respectto flange 29 of the switch arm 17 and the flange 34 of actuating crank33, a limited resilient relationship exists between actuating crank 33and switch arm 17 which may become a positive drive as soon as theflange 34 encounters the closely spaced flange 29 as a result of initialrotation of the crank 33. By this means, movement in the clockwisedirection, for example of actuating crank 33 about the fixed pin 19,results in downward pressure on the end 31 of spring 32 exerted byflange portion 34 which causes end 36 of spring 32 to exert a downwardforce on flange portion 29 on switch arm 17, thereby to gradually buildup a torsional force in the clockwise direction on switch arm 17 whicheventually overcomes the holding force of magnet 20 so that the controldevice contact will move to the closed poistion after this predeterminedrelative lost motion between the actuating crank 33 and switch arm 17.If desired, suitable notches could be placed in the ends of flangedportions 29 and 34 to hold the ends 30 and 31 of spring 32 in position.

Armature 25 is operatively related momentarily to the actuating crank 33by means of an abutment member 37 mounted on armature 25 which isengageable with a pivotally mounted pawl member 38 pivoted to actuatingcrank 33 by a pin 39. Pivotally mounted pawl 38 is biased in theclockwise direction against crank 33 through its projection 43 bytorsional reset spring 40, one end of which engages the pin 41 supportedin crank 33 and the other end of which engages a projecting portion 42forming an integral part of the pawl 38.

When the circuit is completed through coil 24, as by an operator closingthe switch 28, armature 25 moves toward the right against the bias ofits return spring 26 so that when its abutment member 37 engages the tipof the pawl 38, a clockwise moment is applied to the actuating crank 33which first produces clockwise movement of the lower spring arm 31 whilethe upper arm 30 applies an increasing downward pressure upon the flange29. After predetermined rotation of crank 33, its flange 34 impacts theswitch arms flange 29 to thereby positively break the bond between thehold-open magnet 2t) and the switcharm armature 21, so that the contacts15 and 16 thus close the energizing circuit for coil 5 of the breakeroperating mechanism and a breaker closing stroke is instantly initiated.

For dependable and foolproof operation, a circuit breaker control devicemust rely upon manual means for initiating an operating sequence only,and thereafter the subsequent portions of the operating cycle mustproceed automatically and inevitably in such a Way that, irrespective ofwhether the operator continues holding the switch 28 closed or instantlyreleases it, he has no power over the further operation of closedcontacts 15 and 16. For this reason, it is necessary that the armaturenow be rendered incapable of maintaining the control device contactsclosed and this condition is fulfilled in the device of our invention byproviding an appropriate overtravel for the armature 25 during which theabutment member 37 rides over the driving tip of the pawl 38. Thisovertravel position of the armature 25 is shown clearly in Fig. 2; andin arriving at this position, it will be understood that the abutment 37rode over the tip of pawl 38 during a corresponding overtravel of theclockwise rotation of crank 33 with respect to the switch arm 17 whichhad been arrested by the hold-close magnet 22, this overtravel beingavailable by virtue of the aforementioned resilient connection betweenthe crank and lever constituted by the torsion spring 32. Accordingly,if the operator maintains the switch 28 closed, the armature and itsabutment 37 continue attracted to the right beyond the switch arm 17 andthe contacts 15 and 16 will be broken at an appropriate later instant bythe action of the breaker operating mechanism, as will be described. Onthe other hand, should the operator instantly release switch 28 todeenergize coil 24, the armature 25 can return harmlessly against itsstop 27 through the pull of its return spring 26 without affecting theclosed switch arm 17; for in this return movement, the returningabutment 37 will merely have rotated the pawl 38 counterclockwise withrespect to the switch actuating crank 33 because the pawl spring 49 isvery light compared to the torsion spring 32 which constitutes theresilient coupling medium between the crank 33 and the switch arm 17. Inother words, the pawl 38 really constitutes a resilient catch whichpermits but a one-way transitory drive between the actuating armature 25and the driven crank 33 of the control device switch arm 17.

Thus, once the control device contact 15 has been closedelectromagnetically by the operator, the only way these contacts can bereopened to cut off the breaker closing coil 5 is by causingcounterclockwise rotation of the crank 33 by means other than, andindependent of, the above described closing means, and the manner inwhich this opening movement is effected automatically will be madeevident as the description proceeds.

Once the contacts 15 and 16 are closed so as to energize the circuitbreaker operating solenoid 5, its armature 6 moves upwardly to drive theactuating tripfree toggle linkage 7. Linkage 7 comprises aforce-transmitting roller 44 which is rotatable about a pin 45 whichconstitutes the knee of the toggle comprising the thrust links 46 and47. The left-hand end of link 46 is pivoted to a guide link 48 throughthe pin 49 while a tripping roller 50 is mounted rotatably about the pin49. Guide link 48 is pivoted to a fixed fulcrum pin 51 at its lefthandend and a resetting spring 52 exerts a clockwise turning moment on thelink 48 so that in normal circumstances the tripping roller 50 lies inthe position shown between a fixed stop 54 and the arcuate tip of thetrip latch 3 so that the upward thrust of armature 6 is translatedthrough the link 47 and lever 2 into a downward pull on the rod 1 to thebreaker-closed position. in order to maintain the breaker in the closedposition, a prop 55 is pivotally supported about a fixed pin 56 and isbiased in the counterclockwise direction to its holding position bymeans of the torsional reset spring 57. Accordingly, during a breakerclosing operation the prop is brushed aside as in Fig. 2, but itinstantly returns to engage the pin 45 and prop the breaker closed atthe end of a full operating stroke as shown in Fig. 3.

If now the trip coil 13 is energized, i. e., with breaker closed, triplatch 8 (which now constitutes the abutment for receiving the end thrustof the toggle linkage through the tripping roller 59 due to the breakeropening spring 3) will be rotated in the clockwise direction about itsfixed shaft 9, thus allowing the guide link 48 to rotatecounterclockwise as the linkage 7 collapses to the left so that thebreaker opens at high speed.

In order to deenergize the breaker solenoid 5 at or near the end of aclosing stroke of the operating mechanism, it is desirable to provide anappropriate mechanical llnkage between the mechanism and the controldevice whereby the latter is caused to reopen its momentarily closedcontact 15. To this end, there is provided a suitable bell crank mountedadjacent the breaker operating mechanism for actuation thereby throughthe agency of the toggle knee pin 45 which is extended outwardly asuitable amount for this purpose. This bell crank 58 is mounted forrocking about a fixed pivot 59 and it carries a connecting member 60pivotally connected to the short arm thereof by a pin 61. For permittingthe already described closing movement of the control device, a lostmotion connection with the control device actuating crank 33 isprovided, as depicted in Fig. l, in the form of a slot 62 formed in thelower end of connecting member 60 about the driving pin 63. It will beobserved that this slot becomes substantially closed, as shown in Fig.2, coincident with the closing of contacts 15 and 16.

At this point it will be understood that clockwise movement of the bellcrank 58 produces a downward motion to the link 61) wherebycounterclockwise rotation is transmitted to the control device crank 33and its switch arm 17 so that the movable contact 15 separates from thefixed contact 16 to effect the cutoff point of the closing coil 5.Accordingly, if, in conventional manner, it were desired only to cut oifthe closing stroke at a constant predetermined pointnear or at the endof the stroke, it would be necessary to provide only the long horizontalportion 64a. of control arm 64 of the bell crank for engagement thereofby some suitable member moving in unison with the mechanism armature 6.In such a case, however, no provision is made for achieving an earliercutoff point in the event of trip-free closing operations wherein thelatch 8 is tripped during the latter part of the breaker closing stroke.

As another feature of the invention then, a variable cutoff arrangement,for minimizing closing slam, is achieved by actuating the bell crank 58rather in accordance with the toggle action by means of the toggle kneepin 45 and by extending the bell crank control arm 64 downwardly in anarcuate tailpiece 65 which renders the bell crank 58 capable of cutting01f the closing circuit at any point in the closing stroke at which atrip-free response occurs. This is because the tailpiece 65, althoughlying closly adjacent the upward arcuate closing sweep of the knee pin45 so as not to be affected thereby except at the end of a normalfull-closing stroke, nevertheless lies directly in the path of this pinsinstant displacement to the left which results whenever the latch 8 istripped, as from a protective relay, during the concluding part of abreaker closing stroke. For example, let it be assumed that the breakerhas been closed in on a short circuit so that the latch 8 is trippedfrom its holding position at a point short of the complete stroke, i.e., at the instant depicted in Fig. 2. At such a moment, the toggle link46 will move generally bodily over to the left (following the guide link48) with the result that the pin 45, after just having ascended alongthe arcuate path a, will now move to the left along the approximate pathb until the toggle links become generally straightened out (the circuitbreaker opening in the meantime), after which the pin 45 will descendalong the path 0 as the links reset back to the normal breakeropenposition illustrated in Fig. 1. Obviously, in following its lateral path1;, the pin 45 will have imparted the necessary clockwise motion to thebell crank 58 so as to instantly open the control device contacts 15 and16 at an earlier point in the stroke than would have occurred had therebeen no trip-free response and the breaker had closed all the way in ona normal power line. Thus, by shrouding the pin 45 by the arcuateextension 65 of the control arm 64, the closing slam of the mechanism isminimized by arranging its power cutoff to take place either preciselyat the end of a normal closing operation, or selectively andautomatically at any point during the closing operation at which thetrip latch 8 might prematurely respond to fault conditions on the line.

It will be observed that the downward arcuate portion 65 of the bellcrank 58 extends down much lower than would be required for anyconceivable premature or trip-free operation and, in accordance with theinvention, this further extension serves another useful function, viz.,that of providing latch-checking insurance which heretofore has beenprovided only by the use of an additional switch arranged in the closingcoil energizing circuit. By way of explanation, and referring to Fig. 3,it will be understood that the knee pin 45 will follow a closing are Aand, for normal tripping from the fully closed position by the latch 8,will follow generally the return path C as determined by the leftwardcollapse of the toggle links 46 and 47 followed by their return to thenormal mechanism-open position of Fig. 1 under the influence of theresetting spring 52 for the guide link 48. It further will be observedthat the crank actuating knee pin 45 follows the same return path aftertripping, irrespective of whether it has been a trip-free closingoperation or a normal tripping operation; in other Words, the trip-freereturn path c of Fig. 2 is the same as the lower portion of the curvedpath C of Fig. 3. It follows, then, that the resetting of the pin 45 toits normal mechanism-open position D is a good indication that the latch8 has properly reset above the trip roller 50, it being well understoodthat it would be futile for the armature 6 to attempt closing or rapidlyreclosing the mechanism without the latch 8 being back in its normalposition to counteract the toggle forces imposed by the breaker openingspring 3. Because the lower end of the arcuate extension 65 constitutesinterference means which prevents the restoration of bell crank 58 underthe influence of its resetting spring 66 until the pin 45 returns toposition D, it will be apparent that not until this safe moment can thecrank 33 of the control device move to reclose the contacts 15 and 16for reenergizing the 6 breaker closing coil 5. Thus, by making itimpossible for the control device contacts 15 and 16 to reclose untilthe operating mechanism has reset, the contacts 15 and 16 are arrangedto function further in the additional latch-checking capacity whichformerly was provided by a special and separate switch. The dottedoutlines of the bell crank 58 and the toggle knee pin 45 in Fig. 3illustrate several positions which the crank must assume as the knee pin45 follows its close-open path A-C.

From the foregoing explanation, it will be appreciated that the rod orlink 60 constitutes mechanical means operated in accordance with thebreaker operating mechanism for automatically controlling the opening,and preventing the reclosing, of the control device contacts 15 and 16,these contacts already having been closed by separate means controlledmanually by an operator or by other suitable means, such as a reclosingrelay.

Furthermore, it will be appreciated that this closing control of theinvention is nonpumping, for it is impossible for an operator to causereclosure of the control device contacts until he first releases themanual switch 28. Coincident with this ensuing return to the left ofarmature 25, it will be understood that the abutment 37 simply brushesby the pawl 38 (which is freely rotatable against its light spring 40 inthis direction) so that the abutment is once again in condition forpicking up its driving relationship with the pawl 38 in response to thenext energization of the control device coil 24.

Those skilled in the art will appreciate that, in carrying out theinvention, the specific control device or switch described here need notnecessarily be employed in conjunction with the above describedmechanical control means associated with the breaker operatingmechanism. For example, any control switch capable of being closed byone means having self-disconnecting properties and reopened by meansindependent from the closing means may be employed with equallybeneficial results.

While there have been shown and described particular embodiments of theinvention, it is not desired that the invention be limited thereto andit is intended in the appended claims to cover all such changes andmodifications as fall within the true spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. An arrangement for controlling the energization of anelectroresponsive device comprising a switch arm movable between oneposition and another position, a crank, yieldable means for operablyrelating said crank and said switch arm, movable motive means, pivotallymounted means movable with said crank and rotatable in one directionfrom a normal position but not in the other direction from said normalposition, said pivotally mounted means being biased toward its normalposition, abutment means movable with said motive means and engageablewith said pivotally mounted means upon actuation of said motive meansfor operably relating said motive means and said crank to cause movementof said switch arm from said one position to the other position, andmeans operatively connected between said switch arm and saidelectroresponsive device for restoring said switch arm to said oneposition in response to a predetermined operation of theelectroresponsive device.

2. A control arrangement for an electric circuit breaker comprisingelectroresponsive means for imparting closing movement to the breaker, aswitch arm movable from one position to another position to control saidelectroresponsive means, a force-transmitting linkage mechanism movablefrom one position toward another position by said electroresponsivemeans for closing the breaker, latching means engageable by said linkageand operable to cause said linkage to collapse to open the breaker, andmeans including a movable control arm disposed for engagement by saidlinkage upon collapse thereof for causing said switch arm to return tosaid one position.

3. A control arrangement for an electric circuit breaker comprisingelectroresponsive means for imparting closing movement to the breaker, aswitch arm movable from one position to another position to control saidelectroresponsive means, a force-transmitting linkage mechanism movablefrom one position by said electroresponsive means, latching meansengageable by said linka e and v le to enable said linkage to collapseand means including a movable control arm having a portion thereofdisposed for engagement by said linkage 7 upon collapse thereof andanother portion thereof disposed for engagement by said linkage uponmovement thereof by said electroresponsi've means for causing saidSwitch arm to return to said one position. 7

4. A control arrangement for an electric circuit breaker comprisingelectroresponsive means for imparting closing movement to the breaker, aswitch arm movable from one position to another position to control saidelectroresponsive means, a force-transmitting linkage mechanism movablefrom one position toward another position by said elect'roresponsivemeans for closing the breaker, latching means engageable by said linkageand operable to cause said linkage to collapse thereby to open thebreaker, and means including a control arm movable from one position toanother position Whenever said linkage collapses for preventing returnof said switch arm from said one position to said another position untilsaid linkage is reset to said one position.

5. An arrangement for controlling the energization of anelectroresponsive device comprising a switch arm movable between oneposition and another position, movable motive means, pivotally mountedmeans operably related with said switch arm and rotatable in onedirection from a normal position, abutment means movable with saidmotive means and engageable with said pivotally mounted means uponactuation of said motive means for operably relating said motive meansand said switch arm to cause movement thereof from said one position tosaid another position, a control arm movable from one position toanother position in response to actuation of said device, and means forcausing movement of said switch arm from said another position back tosaid one position in response to movement of said control arm to saidanother position.

6. An arrangement for controlling a biased open electric circuit breakercomprising electroresponsive means for imparting closing movement to thebreaker, a switch arm movable from one position to another position forenergizing said electroresponsive means, motive means, pivotally mountedmeans operably related with said switch arm, abutment means movable withsaid motive means and engageable with said pivotally mounted means uponactuation of said motive means to cause movement of said switch arm tosaid another position for energizing said electroresponsive means, alinkage mechanism normally disposed for engagement by saidelectroresponsive means and movable thereby to impart closing movementto the breaker, a control arm disposed for engagement by said linkageupon movement thereof by said electroresponsive means, and meansinte'rrela'ting' said control arm and said switch arm to cause saidswitch arm to move back from said another position upon actuation ofsaid control arm by said linkage.

7. An arrangement for controlling a biased open electric circuit breakercomprising electroresponsive means for imparting closing movement to thebreaker, a switch arm movable from one position to another position foractuating said electroresponsive means, motive means, pivotally mountedmeans operably related with said switch arm, abutment means movable withsaid motive means and engageable withv said pivotally mounted means uponactuation of said motive means to cause movement of said switch arm tosaid another position for actuating said electroresponsive means, alinkage mechanism normally disposed for engagement by saidelectrore'sponsive means and movable thereby to close the breaker, saidlinkage being collapsible to cause the breaker to open, a control armdisposed for engagement by said linkage and movable thereby when saidlinkage collapses, and means "controlled by said control arm for causingmovement of said switch arm back to said one position.

8. An arrangement for controlling the energization of anelect'roresponsive trip-free operating mechanism having a collapsibleforce-transmitting structure comprising a control device including aswitch arm movable between a first and a second position, said switcharm when in said second position effecting energization of saidelectroresponsive mechanism, actuating means for driving said switch armfrom said first to said second position, and means independent of saidactuating means and operated from said force-transmitting structure inresponse to collapse of said force-transmitting structure for returningsaid switch arm back to said first position.

9. In combination, an electroresponsive trip-free operating mechanismcomprising a latch-restrained collapsible force-transmitting structure,an arrangement for controlling said e'lectrorespons'ive mechanismcompris ing a control device including a switch member movable from afirst to a second position to effect energization of saidelectrorespons'ive mechanism, actuating means for moving said switchmember from said first to said second position, a control linkageoperatively coupled to said switch member and actuable to return saidswitch memher from said second to said first position, said controllinkage having a position for blocking switch member movement from saidfirst to said second position, and interference means coupled betweensaid force-transmitting structure and said control linkage and operableto maintain said control linkage in said blocking position whenever saidforce-transmitting structure is collapsed whereby to preventenergization of said mechanism whenever said structure is collapsed.

References Cited in the file of this patent UNITED STATES PATENTS

